Method of producing magnesium carbonate.



e. slssoN. METHOD OP PRODUGING MAGNESIUM GARBONATE.

APPLICATION FILED 0GT.28,1907.

Patented Sept. 28,1909.

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m1 Se 5 UNITED STATES PATENT oEEIoE.

GEORGE SISSON, QF NEWCASTLE-UPON-TYNE, ENGLAND.

METHOD' DF PRODUCING MAGNESIU'H ABBONATE.

To 'all whom it may concern:

Be it known that I, GEORGE SissoN, a subject of the King of- Great Britain'and Ireland, and a resident of Newcastle-upon- T ne Envland have invented a' new and .D 9

useful Improved Method of'Producing Hydratedv Carbonate of Magnesium, of which the following is a specification.

This invention relates to the production of hydrated magnesium carbonate commonly known as and hereinafter referred to as carbonate of magnesium which is especially ap plicable' for industrial purposes, as, for example, for use as a heat insulating coverino, and which is cheaply produced in a simple manner.

-In carrying this invention into effect I- produce the desired carbonate of magnesium by earbonating with or by means of carbon dioxid'in the manner hereinafter'described a'slurry of crude magnesia hydrate which is produced in Ithe known manner by calcining dolomite and slaking it in fresh water, and then treating such l.calcined and slaked dolomite with seawater until the lime is dissolved and removed asealcium ehlorid and replaced by the-magnesia precipitated 'u or derived from the seawater.-

In the accompanying drawings Figure' 1 shows in side. elevation and Fig. 2 in plan -an arrangement of apparatus which-may be used.

A is a tank in which the calcined dolomite is slaked and`-agitated and from which it overflows into the irst'settling tank B. C und D are further like settling tanks, C b eing higher. than B, vand D higher than C. Fresh sea -water is fed to the Dthrough from D can discharge into C through pipe E1; the seawater from C can discharge intol'B through. ipe

EL', and the water from -B'can be runV o to waste through pipe- Ea. These different' K vpipes are controlled by valves o1' cocks as desired, and tanks' B and C are provided with centrifugal elevators F F1 by means of-whieh the' sedimented 'slurry can be discharged from B-to C and from C- to D. The tank B visrfilled with slaked dolomite from A andA with sea waterfrom tank C or which has been otherwise added, -After standing for 'about two or three hoursithe water lfrom tank B is run oif and replaced by water from C and the sedimented slurry from B is raised or transferred to C where it is mixed wlthand where lt'ls again allowed to settle Specification of Letters Patent Patented Sept. 2.8, 1.909. Appnation filed october 2s, 1901. serial no. 399,439.

for about two to three hours in' presence of sea water which has been drawn from tank D. lts place in tank B is now taken by a fresh charge of slaked dolomite. The dolomite in C is 'elevated to tank D 'where it meets clean sea water, and is replaced by the slaked charge in B which is in turn replaced by a new charge. After sett-lement in the highest tank D this part of. the treatment is completed and ,the slurry is drawn off. for further-treatment. fromA the highest `tank it is advantageousto lirst ,draw olf the water from the tank and transfer it to the ,tank C. The slurry from tank D. discharges'throughV a pipe G into a sludge washer H Where it 1s mixed and In drawing oil the slurry agitated with a suiiicient quantity of fresh f water to dissolve and remove the 'hlorids This washing water may be led into the -washer from and be the 'water expressed by filtration ofthe finally producedcarbonate in the filter J. J1 is the pipe by whlch such water is led from the filter to the washer H. K is asettling tank for the washed hydrate 1n communication with H throughpipe H1 and having a Waste discharge outlet 'K1. The settled washedhydrate is then elevated through-a pipe L having two branches L1 and L2. L1 leads to a carbonating tank M, where, brought to the consistency of milkby water, the hydrate has carbon di-oxid vbubbled through' it, the carbon dioxid being supplied through 'a pipe N. The carbonatmgtreatment'is continued until the mag-4 nesium hydrate is converted lnto b1carbo11 ate of magnesium and is dissolved. 'The solution of bi-earbonate thus obtained 1s led to a filter press O and after ltratlon therein for the separation `of insoluble impurities 1s led to a tank P.- Into this tank P the branch L2 -of the pipe ,Ll discharges. the proper quantity'4 ofthe hyd-rate slurry from excess carbon di-oxid tocarbonate the hydrate slurry, precipitatin as carbonate itself and earbonating Vthe hy rate slurry so that the whole produce is carbonate of magne- The bi-earbonate so ution gives up its' sium. This action is facilitated by heat which may be'inexhaust. steam supplied through the 'pipe Q. vJ is the ilter press in which -the carbonate formed in P 1ssepal rated. -A iner and lighter product 1s o`btained in this manner than would be obtained by' treating the magnesium hydrate with carbon di-oxidtoonly such an eentjv 'as to directly produce magnesium carbo lite.

, may then take place.

The carbon dioxid for converting the magnesla hydrate into carbonate or bl-carbonate -may be obtained from the kiln in which the dolomite is calcined.

The slaked dolomite' should preferably lic for some hours before being treated with sea Water'for the removal of lime.

Carbonate of magnesium produced -as above described may have incorporated or mixedwith it asbestos or other fibers suitable for the use to Which it is to be put. Such admixture of fiber preferably takes place before filter-pressing, but may take place at any other subsequent stage.

For some purposes the dried product may be ground or pulverized.

-If desired carbonate produced according to this invention and With or Without the admixture of fibrous or other desired matedioXidA until magnesium bi-carbonate is formed and dissolved, then adding further magnesium hydrate to the solution of bicarbonate to cause the bi-carbonate to give up one-half of the carbon di-oxid contained therein and thereby producing a precipitate of magnesium carbonate, substantially as described.

2. The process of producing carbonate of magnesium, which consists in treating slaked calcined dolomite with sea Water until the lime is removed and replaced by magnesia, then treating thc resulting slurry with carbon dioxid until itis converted into bi-carbonate and adding the so formed bi-carbonate solution to a sufiicient or required quant-ity of the untreated slurry, substantially as and in the manner described.

3. The process of producing carbonate of magnesiumvhich consists in calcining dolomite, slaking it with fresh Water, treating the slaked dolomite with sea Water until the lime is removed and replaced by magnesia, treating the resulting slurry with carbon dioXidobtained from the calcining kiln until it is converted into bi-carbonate, and then adding the so formed bi-carbonate solution to a sufiicientor required quantity of the untreated slurry, all substantially as and in the manner hereinbefore described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses.

GEO. SISSON.

Witnesses:

JOHN BOWMER, NEIL BRODIE. 

